We believe that the planned retirement of the Space Shuttle fleet after the flight of STS-135 next month will create an unacceptable flight risk for maintaining safe and reliable operations of the International Space Station (ISS). As you well know, the shuttles are the only spacecraft that can provide independent spacewalks for critical ISS repairs.

If an incident or life support failure rendered the ISS uninhabitable, repair spacewalks to restore operations would not be possible from the space station. In a worst case scenario, deterioration and loss of systems on an abandoned ISS could result in an uncontrolled, catastrophic reentry with risks to populated areas around the world. This would have significant ramifications to foreign relations and liability for the United States, Russia and the other countries who participate as partners on the International Space Station. The recent near miss of space debris, which caused the ISS astronauts to seek shelter in the Soyuz spacecraft, is a reminder that a catastrophic accident is a stark possibility.

This issue was the subject of a commentary article we co-authored, published in the June 12th edition of the New York Daily News, which is enclosed.

The Space Shuttle fleet is the only spacecraft, now operating or under development, that is equipped with the airlocks, life support supplies and robotic arm needed to support the required two-person spacewalking repair crews. We believe the Space Shuttle fleet should be kept in service to provide the capability of independent repair spacewalks in the event that the International Space Station is crippled by a systems failure or accident. The Space Shuttles would also be available to support one or two logistics and science missions per year, provide unmatched capacity to return components and scientific experiments to Earth (with low gravitational loads on crew and cargo during reentry) and extend the reliability of space station operations with a Service Life Extension Program.

The capability of the Space Shuttles to provide the independent repair spacewalks, critical for restoring operations on a disabled ISS, would also be vital for protecting the ISS cargo and crew transport business of the emerging commercial space industry. Keeping the shuttle fleet in service would also comply with a new, internationally accepted flight criteria that we believe should be established: Any object placed in orbit that is too large for an uncontrolled reentry must have a spacecraft available to support independent EVA repairs.

To maintain this vital life safety margin for long-term ISS operations we are requesting the following:

* In these hearings, Congress should consider passing emergency legislation ordering NASA to halt all work on modifying the Space Shuttle fleet for museum display. Atlantis, Discovery and Endeavour should be stored at Kennedy Space Center in the Orbiter Processing Facility and maintained in such a manner as to keep them flightworthy. Moreover, the Vehicle Assembly Building, Crawler-Transporters, Launch Complex 39-A, Shuttle Landing Facility and other facilities and support equipment needed for Space Shuttle operations should be maintained in place to support future Space Shuttle flights.

* NASA and its International Space Station partners should consider the shared responsibility of developing funding solutions for the continued operation of the Space Shuttle fleet to ensure the long-term safety of space station operations. NASA led plans, as well as commercial alternatives to operate the shuttles commercially, should be presented to Congress and considered to reduce costs and budget impacts.

* To avoid any gap in providing independent repair spacewalks as a safety contingency for the space station, Congress, NASA and the ISS partners should evaluate the option of postponing the launch of STS - 135 until more external fuel tanks and other parts can be built to support additional shuttle flights in 2012.

We appreciate your consideration of our recommendation for NASA and Congress to take immediate action to reverse the retirement of the Space Shuttles. The Space Shuttles are the only solution for restoring space station operations with independent spacewalk repair capabilities. Given the risks and liabilities for NASA and the ISS partners if the International Space Station is crippled by a systems failure or accident, the Space Shuttles are too valuable an asset to be retired into museums. Sincerely,

Why we must save the space shuttle: If the Int'l Space Station is disabled, we need a rescue fleet
BY CHRISTOPHER KRAFT AND SCOTT SPENCER, NEW YORK DAILY NEWS

Sunday, June 12, 2011

For more than 10 years, space crews from the United States, Russia and other countries have successfully lived and worked year round, in six-month shifts, on the International Space Station, where they have conducted scientific research. In the coming years, that work will continue - but with a crucial safeguard missing: the space shuttle fleet that gives human beings a unique capability to fix the space station's guidance system and rocket thrusters in the event of a terrible failure.

The shuttles are now about to retire - all of them, with no true replacements. This is an extremely dangerous development.

Loss of control of the space station would mean a catastrophic reentry into the Earth's atmosphere of the massive structure - the largest object ever placed in orbit around the Earth, measuring over three football fields long and weighing more than 400 tons.

The tons of falling debris that would survive reentry would pose an unprecedented threat to populated areas around the world.

Such an international catastrophe would have significant ramifications for foreign relations and liability for the United States, Russia and the other countries who participate as partners on the space station.

To be sure, the space station has numerous, triple-redundant life support and control systems that makes such a total technical failure unlikely. However, to say that it is so redundant that it could never happen ignores the tragic lessons learned due to the overconfidence in fail-safe technology in disasters throughout history, from the sinking of the Titanic to the nuclear reactor crisis in Japan.

In fact, the numerous space station backup systems offer little margin of safety in the event of damage from a fire, space junk impact or a potential collision from the more frequent docking of manned and unmanned commercial spacecraft resupply missions.

If the life support, guidance systems or rocket thrusters are damaged, the station could need a rapid rescue mission to stay in orbit. And as repair vehicles, the space shuttles have unique capabilities.

It's true that pallets on the space station are packed with spare parts needed for critical repairs, but none of them could be installed to repair and regain control and use of the $100 billion space station if it is deemed uninhabitable for repair crews. In that case, an independent repair spacecraft will be needed. And the Russian Soyuz space capsules and other commercial space capsules that are intended to replace the space shuttles lack the life support systems needed for the multiple six-hour repair spacewalks.

Only the space shuttles have the vital airlocks and life-support supplies - as well as the robotic arm that is needed to move the hardware necessary for the required two-person spacewalking repair crews.

Before the last scheduled shuttle flight lifts off early next month, an urgent discussion needs to take place between the United States and its International Space Station partners to keep the shuttle fleet in service to provide a vital safety margin for repairing the space station in the event of a critical systems failure.

In fact, to prevent any gap in this crucial repair capability, we urge NASA to delay the last shuttle launch so that additional external fuel tanks and other parts can be built to support additional shuttle flights in 2012.

We also request that Congress hold hearings on this matter. The space shuttle fleet provides the only insurance against a catastrophic reentry of the space station. With such valuable equipment in orbit - and the dangers should that equipment fall to Earth - it is never wise to play Russian roulette in space.

Kraft is the former director of NASA's Manned Spaceflight Center in Houston. Spencer is a transportation management consultant in Wilmington, Del.